Preparation method of manganese-rich positive electrode precursor, manganese-rich positive electrode precursor and application

Abstract

The application provides a preparation method of a manganese-rich positive electrode precursor, the manganese-rich positive electrode precursor and application. The preparation method comprises the following steps: performing at least one alkali washing treatment on a manganese-rich positive electrode precursor product obtained after a coprecipitation reaction, and then performing at least one water washing treatment to obtain the manganese-rich positive electrode precursor; wherein the alkali washing liquid of the alkali washing treatment comprises a first reducing agent and an alkaline substance, and the water washing liquid of the water washing treatment comprises a second reducing agent and water. The preparation method provided by the application adds a reducing agent in the washing stage, which can effectively remove impurities such as Na and S, reduce the content of impurities, effectively inhibit the precipitation of manganese on the surface of the manganese-rich positive electrode precursor particles, and the reducing agent is not easy to remain in the precursor particles, does not introduce new impurities to reduce the quality of the precursor product, and does not bring additional processing costs, thereby significantly improving the electrochemical performance of the manganese-rich positive electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to a preparation method of a manganese-rich positive electrode precursor, the manganese-rich positive electrode precursor and application thereof. BACKGROUND

[0002] In the field of lithium ion battery material preparation, manganese-rich precursors (binary manganese-rich or ternary manganese-rich precursors containing more than 30 wt% of manganese) are important positive electrode material precursors. The positive electrode materials prepared from the manganese-rich precursors have high energy density, high working voltage and good capacity retention rate, and thus are widely used in the fields of electric vehicles, mobile electronic devices and the like.

[0003] CN111498908A discloses a preparation method of a spherical manganese-rich ternary precursor, which comprises the following steps: first, a nickel-cobalt-manganese sulfate mixed solution is prepared by mixing and dissolving nickel sulfate, cobalt sulfate and manganese sulfate; then, the nickel-cobalt-manganese sulfate mixed solution and a precipitant solution are added into a reaction kettle in parallel flow, and a complexing agent is added in parallel flow at the same time; the pH value is controlled to be 6.8-10.0, the reaction temperature is controlled to be 40-80℃, and the stirring speed is controlled to be 200-800 r / min; after the solution dripping is completed, the suspension is aged in the reaction kettle for 5-20 h; after the aging is completed, the suspension is filtered and washed; and finally, the spherical manganese-rich ternary precursor is obtained by vacuum drying at 80℃ for 10-20 h, which lays a good foundation for the preparation of lithium-rich manganese-based positive electrode materials.

[0004] However, the oxidation and precipitation of manganese elements become an important problem during the preparation and storage of the manganese-rich precursors. The precipitated manganese oxides may block the diffusion channels of lithium ions in the positive electrode materials, increase the internal resistance of the battery, and thus reduce the charge and discharge performance of the battery; the oxidation and precipitation of manganese may also cause changes in the structure of the material, possibly leading to micro-short circuits in the battery, increasing the risk of thermal runaway of the battery, and thus causing safety problems; in addition, the oxidation and precipitation of manganese may also damage the structural integrity of the positive electrode material, reducing the cycle life of the battery.

[0005] In order to solve this problem, researchers have conducted a lot of research work to try to find an effective method to inhibit the oxidation and precipitation of manganese. At present, although some methods have been proposed, such as adding stabilizers, performing surface coating or chemical doping, etc., the effects of these methods are often affected by many factors such as temperature, time, type and concentration of additives, coating or doping process, etc., and it is difficult to achieve ideal effects. At the same time, these methods may also introduce impurities, increase the preparation cost, and reduce the production efficiency.

[0006] As CN110963533A discloses a preparation method of a lithium-rich manganese-based positive electrode material precursor, comprising the following steps: step one, raw material selection; step two, impurity removal by filtration; step three, parallel flow reaction; step four, product treatment; step five, sample quality inspection; in the above step one, a metal salt solution, an ammonia-alkali mixed solution and a protective gas are selected as raw materials, wherein manganese salt, nickel salt and cobalt salt are dissolved in deionized water in a certain stoichiometric ratio, an appropriate amount of reducing agent is added, and stirring is performed for a certain time to prepare a metal salt solution, and an ammonia-alkali mixed solution of a certain concentration of sodium hydroxide and ammonia water is prepared. Although a reducing agent is added in this document, this method may also introduce impurities, increase the preparation cost and reduce the production efficiency.

[0007] Therefore, it is still a technical problem to be solved at present to develop a method for inhibiting the oxidation and precipitation of manganese in a manganese-rich positive electrode precursor. SUMMARY

[0008] In view of the deficiencies in the prior art, the purpose of the present application is to provide a preparation method of a manganese-rich positive electrode precursor, a manganese-rich positive electrode precursor and an application. The preparation method provided by the present application adds a reducing agent in the washing stage, which can not only effectively remove impurities such as Na and S and reduce the content of impurities, but also effectively inhibit the precipitation of manganese on the surface of the manganese-rich positive electrode precursor particles, improve the particle morphology and stability, and the reducing agent is not easy to remain in the precursor particles, which will not introduce new impurities to reduce the quality of the precursor product, nor will it bring additional processing cost, thereby improving the electrochemical performance of the manganese-rich positive electrode material and enhancing the safety performance of the lithium ion battery.

[0009] To achieve the purpose of the present application, the following technical solutions are adopted:

[0010] In a first aspect, the present application provides a preparation method of a manganese-rich positive electrode precursor, comprising the following steps:

[0011] The manganese-rich positive electrode precursor product obtained after the coprecipitation reaction is subjected to at least one alkali washing treatment, and then subjected to at least one water washing treatment to obtain the manganese-rich positive electrode precursor.

[0012] Among them, the alkali washing liquid of the alkali washing treatment includes a first reducing agent and an alkaline substance, and the water washing liquid of the water washing treatment includes a second reducing agent and water.

[0013] It should be noted that the present application does not make special limitations on the types of the first reducing agent and the second reducing agent, and the types of reducing agents that can be used to inhibit the precipitation of manganese oxide are applicable to the present application, for example, the first reducing agent and the second reducing agent each independently include but are not limited to at least one of glucose, oxalic acid, hydrazine hydrate, sodium sulfite, citric acid, ascorbic acid or D-isoascorbic acid.

[0014] The preparation method provided by the application adds a reducing agent in the washing stage, and the reducing agent is added in the alkali washing and water washing processes, which can effectively remove impurities such as Na and S, reduce the content of impurities, effectively inhibit the precipitation of manganese oxide on the surface of the manganese-rich positive electrode precursor particles, improve the particle morphology and stability, and the reducing agent is not easy to remain in the precursor particles, does not introduce new impurities, and does not bring additional processing cost, thereby significantly improving the electrochemical performance of the manganese-rich positive electrode material.

[0015] In the application, the reducing agent needs to be added in the alkali washing and water washing processes in the washing treatment process, so as to achieve the purpose of inhibiting the precipitation of manganese oxide, improving the crystallinity of the material, and avoiding the introduction of too many impurities, which can obviously improve the quality of the precursor; if the reducing agent is added in the coprecipitation reaction process, the precursor particles will adsorb a certain amount of reducing agent during the growth process, so that the reducing agent remains in the precursor particles, which leads to the introduction of new impurities and reduces the quality of the precursor product, and brings additional cost of processing the reducing agent.

[0016] The following is a preferred technical solution of the application, but is not a limitation on the technical solutions provided by the application. Through the following preferred technical solution, the technical purpose and beneficial effects of the application can be better achieved and realized.

[0017] Preferably, the chemical formula of the manganese-rich positive electrode precursor product is Mn x M 1-x (A) z , 0.3≤x≤0.95, 1≤z≤2, M includes a transition metal element, and A includes a hydroxyl ion or a carbonate ion.

[0018] For example, x can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 0.95, etc.; z can be 1, 1.5 or 2, etc.; but not limited to the listed values, other values not listed in the range are also applicable.

[0019] In the application, the specific type of M element in Mn x M 1-x (A) z is not specially limited, and can be combined with manganese as an M element of a positive electrode precursor material, and the application is applicable, including but not limited to at least one of Ni, Co, Fe, Cu or Al, etc.

[0020] Preferably, the number of alkali washing processes is ≥2 times, for example, 2 times, 3 times, 4 times or 5 times, etc.

[0021] Preferably, the number of water washing treatments is ≥2, such as 2, 3, 4, or 5, etc.

[0022] In the present application, the number of alkali washing treatments and the number of water washing treatments are both ≥2, which is more conducive to fully removing the small amount of Na / S impurities wrapped in the co-precipitation process, and making the trace amount of manganese oxide already precipitated on the surface of the particles be fully reduced, thereby improving the quality of the precursor product.

[0023] Preferably, the temperature of the alkali washing treatment and the temperature of the water washing treatment are each independently 10-40℃, such as 10℃, 20℃, 30℃, or 40℃, etc.

[0024] Preferably, the mass fraction of the first reducing agent in the alkali washing solution is 0.1-10wt%, such as 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, or 10wt%, etc.

[0025] In the present application, the mass fraction of the first reducing agent in the alkali washing solution is 0.1-10wt%, which can better realize the beneficial effect of inhibiting the precipitation of manganese oxide and improving the crystallinity of the material at a lower cost.

[0026] Preferably, the mass fraction of the alkaline substance in the alkali washing solution is 2-20wt%, such as 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, or 20wt%, etc., but not limited to the listed values, other unlisted values within this range are also applicable.

[0027] In the present application, the specific types of alkaline substances are all conventional technical choices, which can be selected from at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, or ammonium bicarbonate, etc.

[0028] Preferably, during each alkali washing treatment, the volume ratio of the manganese-rich positive electrode precursor product to the alkali washing solution is V 产物 :V 碱洗液 =1:(1-5), such as 1:1, 1:2, 1:3, 1:4, or 1:5, etc.

[0029] Preferably, the washing time of each alkali washing treatment is each independently 2-8h, such as 2h, 3h, 4h, 5h, 6h, 7h, or 8h, etc.

[0030] Preferably, the mass fraction of the second reducing agent in the water washing solution is 0.5-15wt%, for example, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt% and the like.

[0031] Preferably, the volume ratio of the manganese-rich positive electrode precursor product to the water washing solution in each water washing process is V 产物 :V 水洗液 =1:(1-5), for example, 1:1, 1:2, 1:3, 1:4 or 1:5 and the like.

[0032] Preferably, the washing time of each water washing process is independently 2-8h, for example, 2h, 3h, 4h, 5h, 6h, 7h or 8h and the like.

[0033] Preferably, after the water washing process, a drying process is performed.

[0034] Preferably, the D50 of the manganese-rich positive electrode precursor is 2-15μm, for example, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm or 15μm and the like, preferably 4-10μm.

[0035] As a preferred technical solution, the preparation method comprises the following steps:

[0036] The manganese-rich positive electrode precursor product Mn x M 1-x (A) z is obtained after the coprecipitation reaction, and at least 2 alkaline washing processes are performed, and the volume ratio of the manganese-rich positive electrode precursor product to the alkaline washing solution in each alkaline washing process is V 产物 :V 碱洗液 =1:(1-5), and the washing time of each alkaline washing process is independently 2-8h;

[0037] Then at least 2 water washing processes are performed, and the volume ratio of the manganese-rich positive electrode precursor product to the water washing solution in each water washing process is V 产物 :V 水洗液 =1:(1-5), and the washing time of each water washing process is independently 2-8h, and after the water washing process, a drying process is performed to obtain the manganese-rich positive electrode precursor with a D50 of 2-15μm;

[0038] wherein 0.3≤x≤0.95, 1≤z≤2, M comprises a transition metal element, and A comprises a hydroxyl ion or a carbonate ion;

[0039] The alkali washing solution includes 0.1-10wt% of the first reducing agent and 2-20wt% of the alkaline substance, and the washing solution includes 0.5-15wt% of the second reducing agent and water.

[0040] It should be noted that the preparation method of the co-precipitation reaction of the manganese-rich positive electrode precursor product in the present application is a conventional technical solution, that is, the preparation method of the manganese-rich positive electrode precursor material (or the conventional preparation method of the manganese-based positive electrode material) can be prepared.

[0041] Exemplarily, the present application provides a preparation method of a manganese-rich positive electrode precursor product, which comprises the following steps:

[0042] The manganese-rich mixed salt solution (i.e., the mixed salt solution including Mn and M according to the chemical formula Mn x M 1-x (A) z The mixed salt solution including Mn and M, the precipitant solution and the complexing agent solution are added into the reaction kettle containing the bottom liquid in a concurrent manner, and the co-precipitation reaction is carried out under a protective atmosphere. After the target particle size is reached, the reaction is stopped, and the manganese-rich positive electrode precursor product to be washed is obtained.

[0043] Optionally, the concentration of the total metal ions in the manganese-rich mixed salt solution is 1-3mol / L, such as 1mol / L, 1.5mol / L, 2mol / L, 2.5mol / L or 3mol / L, etc. The specific types of salt solutions include but are not limited to at least one of chloride, nitrate, sulfate or acetate, but are not limited to the listed values. Other values not listed within this range are also applicable.

[0044] Optionally, the mass fraction of the precipitant solution is 20-40wt%, such as 20wt%, 25wt%, 30wt%, 35wt% or 40wt% etc. The precipitant includes but is not limited to at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate, but is not limited to the listed values. Other values not listed within this range are also applicable.

[0045] Optionally, the mass fraction of the complexing agent solution is 10-25wt%, such as 10wt%, 15wt%, 20wt% or 25wt% etc. The complexing agent includes but is not limited to at least one of ammonium bicarbonate, ammonia, oxalic acid or ethylenediaminetetraacetic acid disodium, but is not limited to the listed values. Other values not listed within this range are also applicable.

[0046] Optionally, the base solution comprises water, a complexing agent and a precipitant, and the pH of the base solution is 11.4-12.6, for example, 11.4, 11.5, 11.6, 11.8, 12, 12.3, 12.5 or 12.6, etc.

[0047] Optionally, the protective atmosphere comprises a nitrogen atmosphere or an inert gas atmosphere (such as an argon atmosphere or a helium atmosphere, etc.).

[0048] Optionally, the reaction temperature of the co-precipitation reaction is 40-70℃, for example, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃ or 70℃, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0049] Optionally, the pH value of the co-precipitation reaction is 9.2-11.4, for example, 9.2, 9.5, 9.8, 10, 10.3, 10.5, 10.8, 11, 11.3 or 11.4, etc., but not only limited to the listed values, other values not listed in this range are also applicable.

[0050] Optionally, the target particle size is the D50 of the manganese-rich positive electrode precursor.

[0051] It can be understood that those skilled in the art can adaptively select and adjust the preparation parameters in the preparation process of the co-precipitation reaction according to actual needs.

[0052] In a second aspect, the present application provides a manganese-rich positive electrode precursor, which is prepared by the preparation method of the first aspect.

[0053] In a third aspect, the present application provides a positive electrode material, which is obtained by mixing and sintering the manganese-rich positive electrode precursor of the second aspect with a lithium source.

[0054] The present application does not make special limitations on the specific preparation process of the positive electrode material, and the conventional preparation process within the reasonable range of those skilled in the art is applicable to the present application.

[0055] Exemplarily, the present application provides a preparation method of a positive electrode material:

[0056] The lithium source and the manganese-rich positive electrode precursor are mixed at a total molar ratio of lithium elements in the lithium source to all metal elements in the manganese-rich positive electrode precursor of (1-1.6):1, and then sintered under an oxygen-containing atmosphere (such as an air atmosphere or an oxygen atmosphere) at a sintering temperature of 800-1200℃ for a sintering time of 8-20h to obtain the lithium-rich manganese-based positive electrode material.

[0057] Further, the lithium source includes at least one of LiOH, CH3COOLi, or Li2CO3.

[0058] In a fourth aspect, the present application further provides a lithium ion battery, which comprises the positive electrode material according to the third aspect.

[0059] It should be noted that, due to the limitation of the length and in order to avoid redundancy, the present application does not list all the applicable point values in the above numerical range, but is not limited to the listed values, and other unlisted values in the above numerical range are also applicable.

[0060] Compared with the prior art, the present application has the following beneficial effects:

[0061] The preparation method provided by the present application adds a reducing agent in the washing stage, and the reducing agent is added in the alkali washing and water washing processes, which can effectively remove impurities such as Na and S, reduce the content of impurities, effectively inhibit the precipitation of manganese oxide on the surface of the manganese-rich positive electrode precursor particles, improve the particle morphology and stability, and the reducing agent is not easy to remain in the precursor particles, which will not introduce new impurities and will not bring additional processing cost, thereby significantly improving the electrochemical performance of the manganese-rich positive electrode material. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 SEM image of the manganese-rich positive electrode precursor provided for Example 1.

[0063] Figure 2 SEM image of the manganese-rich positive electrode precursor provided for Comparative Example 1. DETAILED DESCRIPTION

[0064] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application, and should not be regarded as specific limitations of the present application.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the terms "comprising" and "having," and any variations thereof, are intended to cover not exclusively including.

[0066] In the description of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified.

[0067] Example 1

[0068] The present embodiment provides a preparation method of a manganese-rich positive electrode precursor, and the preparation method is as follows:

[0069] In step S1, a mixed metal salt solution (a nickel-manganese-containing sulfate solution) is prepared according to the molecular formula Ni 0.35 Mn 0.65 (OH)2, with a total metal ion concentration of 2 mol / L; a sodium hydroxide solution (a precipitant solution) with a mass fraction of 32 wt% is prepared; and an ammonia water solution with a mass fraction of 16 wt% is prepared.

[0070] A reaction bottom solution with pH = 12.2-12.4 and ammonia water concentration of 6-7 g / L is prepared by using liquid alkali, concentrated ammonia water and pure water; under the protection of a nitrogen atmosphere, the prepared mixed metal salt solution, sodium hydroxide solution and ammonia water solution are respectively added into a reaction kettle containing the bottom solution at a flow rate of 4 L / h, 1 L / h and 0.32 L / h in a uniform and parallel flow manner to perform a co-precipitation reaction; the reaction temperature of the co-precipitation reaction is controlled to be maintained at 58±1℃, the stirring speed is 400 rpm, the pH in the growth stage is maintained at 10.4-10.8, and the ammonia concentration is maintained at 6-7 g / L; when the particle size D50 reaches 5 μm, the feeding is stopped, and a manganese-rich positive electrode precursor product Ni 0.35 Mn 0.65 (OH)2 is obtained.

[0071] In step S2, an alkali washing solution A is prepared according to a mass ratio of sodium hydroxide:sodium carbonate:ascorbic acid: pure water = 10:3:2:85, and a water washing solution B is prepared according to a mass ratio of citric acid:ascorbic acid: pure water (deionized water) = 2:3:95, which are respectively used as detergents for alkali washing and water washing.

[0072] The manganese-rich positive electrode precursor product obtained in step S1 is placed and transferred to a washing device after the supernatant is removed, and is subjected to three times of alkali washing treatment with the alkali washing solution A (the volume ratio of the washing material to the alkali washing solution A is 1:5), and then is subjected to three times of water washing treatment with the water washing solution B (the volume ratio of the washing material to the water washing solution B is 1:5); after the washing treatment is completed, the solid-liquid separation is performed, and then the product is transferred to an oven and is dried at 100℃, so that the manganese-rich positive electrode precursor product is obtained.

[0073] Example 2

[0074] The present embodiment provides a preparation method of a manganese-rich positive electrode precursor, and the preparation method is as follows:

[0075] In step S1, a mixed metal salt solution (a nickel-manganese-containing sulfate solution) is prepared according to the molecular formula Ni 0.35 Mn 0.65Prepare a mixed metal salt solution (containing nickel and manganese sulfate solution) with a total metal ion concentration of 1 mol / L; prepare a 20 wt% sodium hydroxide solution (precipitant solution); prepare a 10 wt% ammonia solution.

[0076] A reaction substrate solution with pH = 12.0–12.2 and ammonia concentration of 6–7 g / L was prepared using liquid alkali, concentrated ammonia, and pure water. Under a nitrogen atmosphere, the prepared mixed metal salt solution, sodium hydroxide solution, and ammonia solution were added to the reactor containing the substrate solution at uniform flow rates of 4 L / h, 1 L / h, and 0.32 L / h, respectively, to carry out a co-precipitation reaction. The reaction temperature of the co-precipitation reaction was maintained at 40 °C, the stirring speed at 250 rpm, the pH during the growth stage at 11.0–11.3, and the ammonia concentration at 6–7 g / L. When the particle size D50 reached 10 μm, the feed was stopped, and the manganese-rich cathode precursor product Ni was obtained. 0.35 Mn 0.65 (OH)2;

[0077] Step S2: Prepare alkaline washing solution A according to the mass ratio of sodium hydroxide:sodium carbonate:citric acid:pure water = 15:5:5:80, and prepare water washing solution B according to the mass ratio of citric acid:oxalic acid:pure water = 1:1:95. These solutions will be used as detergents for alkaline washing and water washing, respectively.

[0078] The manganese-rich cathode precursor product obtained in step S1 is allowed to stand, and the supernatant is drawn off and transferred to a washer. It is then subjected to two alkaline washing treatments with alkaline washing solution A (the volume ratio of the material to be washed to alkaline washing solution A is 1:1), followed by two water washing treatments with water washing solution B (the volume ratio of the material to be washed to water washing solution B is 1:1). After the washing treatment is completed, the solid and liquid are separated and transferred to an oven for drying at 100°C to obtain the manganese-rich cathode precursor product.

[0079] Example 3

[0080] This embodiment provides a method for preparing a manganese-rich cathode precursor, the method of which is as follows:

[0081] Step S1, according to the molecular formula Ni 0.35 Mn 0.65 Prepare a mixed metal salt solution (containing nickel and manganese sulfate solution) with a total metal ion concentration of 2 mol / L; prepare a 32 wt% sodium hydroxide solution (precipitant solution); prepare a 16 wt% ammonia solution.

[0082] The reaction bottom solution with pH = 12.2-12.4 and ammonia water concentration of 6-7 g / L is prepared by mixing liquid alkali, concentrated ammonia water and pure water; under the protection of nitrogen atmosphere, the prepared mixed metal salt solution, sodium hydroxide solution and ammonia water solution are respectively added into the reaction kettle containing the bottom solution at a flow rate of 4 L / h, 1 L / h and 0.32 L / h in a uniform and parallel flow manner to carry out the coprecipitation reaction; the reaction temperature of the coprecipitation reaction is controlled to be maintained at 58±1℃, the stirring speed is 400 rpm, the pH in the growth stage is maintained at 10.4-10.8, and the ammonia concentration is maintained at 6-7 g / L; when the particle size D50 reaches 5 μm, the feeding is stopped, and the manganese-rich positive electrode precursor product Ni 0.35 Mn 0.65 (OH)2;

[0083] In step S2, the alkali washing solution A is prepared according to the mass ratio of sodium hydroxide:sodium carbonate:ascorbic acid: pure water = 5:3:10:82, and the water washing solution B is prepared according to the mass ratio of citric acid:ascorbic acid: pure water = 5:5:90, which are used as the washing agent for alkali washing and water washing, respectively;

[0084] The manganese-rich positive electrode precursor product obtained in step S1 is placed, and after the supernatant is removed, it is transferred to a washing device for three times of alkali washing treatment with the alkali washing solution A (the volume ratio of the washing material to the alkali washing solution A is 1:3), and then three times of water washing treatment with the water washing solution B (the volume ratio of the washing material to the water washing solution B is 1:3). After the washing treatment is completed, the solid-liquid separation is carried out, and then the product is transferred to an oven for drying at 100℃, thereby obtaining the manganese-rich positive electrode precursor product.

[0085] Example 4

[0086] The difference between this example and example 1 is that the chemical general formula of the manganese-rich positive electrode precursor product in this example is Ni 0.3 Co 0.1 Mn 0.6 (OH)2.

[0087] In the preparation method, the mixed metal salt solution (sulfate solution containing nickel and manganese) is prepared according to the molecular formula Ni 0.3 Co 0.1 Mn 0.6 (OH)2.

[0088] The rest of the preparation method and parameters are consistent with those of example 1.

[0089] Example 5

[0090] The difference between this example and example 1 is that in step S2 of this example, the alkali washing solution A is prepared according to the mass ratio of sodium hydroxide:sodium carbonate:ascorbic acid: pure water = 10:3:15:72, that is, the mass fraction of the reducing agent in the alkali washing solution is adjusted to 15 wt%.

[0091] The rest of the preparation method and parameters remain the same as in Example 1.

[0092] Example 6

[0093] The difference between this example and Example 1 is that in step S2 of this example, the water washing solution B is prepared according to the mass ratio of citric acid: ascorbic acid: pure water = 6:9:85, i.e. the mass fraction of the reducing agent in the water washing solution is adjusted to 15wt%.

[0094] The rest of the preparation method and parameters remain the same as in Example 1.

[0095] Example 7

[0096] The difference between this example and Example 1 is that in step S2 of this example, only one alkaline washing treatment and one water washing treatment are performed.

[0097] The rest of the preparation method and parameters remain the same as in Example 1.

[0098] Comparative Example 1

[0099] The difference between this comparative example and Example 1 is that in step S2 of this comparative example, the alkaline washing solution does not contain a reducing agent (i.e. the mass fraction of the alkaline substance remains unchanged, and the amount of water added is adjusted), and the water washing solution also does not contain a reducing agent (i.e. it is pure water).

[0100] The rest of the preparation method and parameters remain the same as in Example 1.

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 1 is that in step S2 of this comparative example, the alkaline washing solution does not contain a reducing agent (i.e. the mass fraction of the alkaline substance remains unchanged, and the amount of water added is adjusted).

[0103] The rest of the preparation method and parameters remain the same as in Example 1.

[0104] Comparative Example 3

[0105] The difference between this comparative example and Example 1 is that in step S2 of this comparative example, the water washing solution does not contain a reducing agent (i.e. it is pure water).

[0106] The rest of the preparation method and parameters remain the same as in Example 1.

[0107] Comparative Example 4

[0108] The difference between this comparative example and Example 1 is that in step S1 of this comparative example, a reducing agent solution is added to the bottom solution of the coprecipitation reaction, and the mass fraction of the specific reducing agent solution (ascorbic acid) is 0.5mol / L.

[0109] In step S2, the alkaline washing solution does not contain a reducing agent (i.e., the mass fraction of the alkaline substance remains unchanged, and the amount of water added is adjusted), and the water washing solution also does not contain a reducing agent (i.e., it is pure water).

[0110] The remaining preparation methods and parameters are consistent with those in Example 1.

[0111] from Figure 1 and Figure 2 It can be seen that the small particles on the surface of the manganese-rich cathode precursor obtained in Example 1 of the present invention are basically eliminated, which indicates that the precipitation of manganese oxide has been significantly suppressed and the particle morphology has been significantly improved; while the manganese-rich cathode precursor obtained in Comparative Example 1 without the addition of a reducing agent in the washing stage has a large number of small particles on its surface, which indicates that the phenomenon of manganese oxide precipitation has not been solved.

[0112] Table 1 shows the Na and S impurity contents in the lithium-rich manganese-based precursors provided in Examples 1-7 and Comparative Examples 1-4.

[0113] Table 1

[0114] Na (ppm) S (ppm) Example 1 40 476 Example 2 47 493 Example 3 43 483 Example 4 44 481 Example 5 42 480 Example 6 43 483 Example 7 78 734 Comparative Example 1 60 538 Comparative Example 2 53 512 Comparative Example 3 51 515 Comparative Example 4 63 579

[0115] [Preparation of cathode materials, battery fabrication, and performance testing]

[0116] Preparation of cathode material: The manganese-rich cathode precursors obtained in Examples 1-7 and Comparative Examples 1-4 were uniformly mixed with lithium hydroxide at a molar ratio of 1:1.5 and sintered in air at 900°C for 15 hours to obtain the corresponding lithium-rich manganese-based cathode material.

[0117] Battery fabrication: The lithium-rich manganese-based cathode materials prepared in Examples 1-7 and Comparative Examples 1-4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were weighed at a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone (NMP) and mixed thoroughly. Then, the slurry was coated onto aluminum foil using a coater and dried in a vacuum drying oven at 80°C for 8 hours. Finally, the aluminum foil was stamped into 1.13 cm thick sheets. 2 A circular shape is obtained to form the positive electrode plate;

[0118] The obtained electrode sheet was used as the positive electrode, the lithium metal sheet as the counter electrode, and the porous polypropylene membrane (Celgard2400) was used as the separator to separate the positive and counter electrodes. The electrolyte composition was: a mixture of 1M LiPF6 and EC, DMC and EMC (EC:DMC:EMC volume ratio = 1:1:1). The CR2032 button cell was assembled in an argon glove box.

[0119] The batteries provided in Examples 1-7 and Comparative Examples 1-4 were subjected to performance tests under the following conditions: the test temperature was 25°C. Using a charge-discharge test system, the batteries were charged at a current of 0.33C to the cutoff voltage of 4.8V, then charged at a constant voltage to a current of 0.05C. After resting for 30 minutes, they were discharged at a current of 0.33C to 2.0V. The capacity obtained in this step was taken as the discharge capacity of the first cycle. The above steps were repeated, and the discharge capacity of the battery in the 100th cycle was recorded. The capacity retention rate in the 100th cycle = discharge capacity in the 100th cycle / discharge capacity in the first cycle. The test results are shown in Table 2.

[0120] Table 2

[0121]

[0122]

[0123] from Figures 1-2 From Table 1, we can obtain:

[0124] As can be seen from the data results of Examples 1-4, the preparation method provided by the present invention produces a manganese-rich cathode precursor with a stable structure, virtually no manganese oxide particles precipitated on the particle surface, and a significantly improved microstructure, thereby enhancing the electrochemical performance of the manganese-rich cathode material and strengthening the safety performance of lithium-ion batteries.

[0125] The data results from Examples 1 and 5 show that if the mass fraction of the first reducing agent in the alkaline washing solution is too high, it will increase the material cost of purchasing the reducing agent and the post-processing cost of the reducing agent. It will also easily introduce a small amount of reducing agent into the precursor particles, resulting in a low performance improvement effect of the lithium-rich manganese-based cathode material.

[0126] The data results from Examples 1 and 6 show that if the mass fraction of the second reducing agent in the washing solution is too high, it will increase the material cost of purchasing the reducing agent and the post-processing cost of the reducing agent. It will also easily introduce a small amount of reducing agent into the precursor particles, resulting in a low performance improvement effect of the lithium-rich manganese-based cathode material.

[0127] The data from Examples 1 and 7 show that the number of alkaline washing and water washing treatments was too small, resulting in excessive Na and S impurities remaining, and the performance improvement effect of the prepared lithium-rich manganese-based cathode material was low.

[0128] As can be seen from the data results of Example 1 and Comparative Examples 1-3, the present invention adds a reducing agent during the washing process, and adds a reducing agent during both alkaline washing and water washing. This can effectively remove Na and S impurities while inhibiting the precipitation of manganese oxides on the surface of manganese-rich cathode precursor particles, ultimately improving particle morphology and stability, thereby simultaneously improving the capacity and cycle performance of lithium-rich manganese-based cathode materials.

[0129] From the data results of example 1 and comparative example 4, it can be seen that, in the process of coprecipitation reaction, although the addition of reducing agent can solve the problem of manganese dissolution to a certain extent, it is easy to cause the reducing agent to remain in the material, leading to performance deterioration, and the capacity and cycle performance of the lithium-rich manganese-based positive electrode material cannot be improved.

[0130] The preparation method provided by the present application adds a reducing agent in the washing stage, and the reducing agent is added in the alkali washing and water washing processes, which can effectively remove impurities such as Na and S, reduce the content of impurities, effectively inhibit the precipitation of manganese on the surface of the manganese-rich positive electrode precursor particles, improve the particle morphology and stability, and the reducing agent is not easy to remain in the precursor particles, which will not introduce new impurities, and at the same time, it also ensures that the content of the lithium-rich manganese-based precursor material is low, and will not bring additional processing cost, thereby improving the electrochemical performance of the manganese-rich positive electrode material and enhancing the safety performance of the lithium ion battery.

[0131] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application, which can be easily thought of by any person skilled in the art, falls within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a manganese-rich cathode precursor, characterized in that, The preparation method includes the following steps: The manganese-rich cathode precursor product obtained after the co-precipitation reaction is subjected to at least one alkaline washing treatment, and then to at least one water washing treatment to obtain the manganese-rich cathode precursor. The alkaline washing solution of the alkaline washing treatment includes a first reducing agent and an alkaline substance, and the water washing solution of the water washing treatment includes a second reducing agent and water. The first reducing agent and the second reducing agent each independently include at least one of glucose, oxalic acid, hydrazine hydrate, sodium sulfite, citric acid, oxalic acid, or D-iso-oxalic acid.

2. The preparation method according to claim 1, characterized in that, The general chemical formula of the manganese-rich cathode precursor product is Mn. x M 1-x (A) z , 0.3≤x≤0.95, 1≤z≤2, M includes transition metal elements, A includes hydroxide ions or carbonate ions.

3. The preparation method according to claim 1, characterized in that, The number of alkaline washing treatments is ≥2 times.

4. The preparation method according to claim 1, characterized in that, The number of water washing treatments is ≥2 times.

5. The preparation method according to claim 1, characterized in that, The temperatures for the alkaline washing treatment and the water washing treatment are each independently between 10 and 40°C.

6. The preparation method according to claim 1, characterized in that, The mass fraction of the first reducing agent in the alkaline washing solution is 0.1~10wt%.

7. The preparation method according to claim 1, characterized in that, The alkaline substance has a mass fraction of 2-20 wt% in the alkaline washing solution.

8. The preparation method according to claim 1, characterized in that, During each alkaline washing process, the volume ratio of the manganese-rich cathode precursor product to the alkaline washing solution is V. 产物 :V 碱洗液 =1:(1~5).

9. The preparation method according to claim 1, characterized in that, Each alkaline washing treatment takes 2 to 8 hours independently.

10. The preparation method according to claim 1, characterized in that, The second reducing agent has a mass fraction of 0.5~15wt% in the washing solution.

11. The preparation method according to claim 1, characterized in that, During each water washing process, the volume ratio of the manganese-rich cathode precursor product to the washing solution is V. 产物 :V 水洗液 =1:(1~5).

12. The preparation method according to claim 1, characterized in that, Each washing process takes 2 to 8 hours independently.

13. The preparation method according to claim 1, characterized in that, After the water washing process, a drying process is performed.

14. The preparation method according to claim 1, characterized in that, The D50 of the manganese-rich cathode precursor is 2~15μm.

15. The preparation method according to claim 1, characterized in that, The D50 of the manganese-rich cathode precursor is 4~10 μm.

16. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: The manganese-rich cathode precursor product Mn obtained after the coprecipitation reaction x M 1-x (A) z Perform at least two alkaline washing treatments. During each alkaline washing treatment, the volume ratio of the manganese-rich cathode precursor product to the alkaline washing solution is V. 产物 :V 碱洗液 =1:(1~5), the washing time for each alkaline washing treatment is 2~8h independently; Then, perform at least two water washing processes. During each water washing process, the volume ratio of the manganese-rich cathode precursor product to the washing solution is V. 产物 :V 水洗液 =1:(1~5), the washing time for each water washing treatment is 2~8h independently, and after the water washing treatment is completed, the drying treatment is performed to obtain the manganese-rich cathode precursor with D50 of 2~15μm; Where 0.3≤x≤0.95, 1≤z≤2, M includes transition metal elements, and A includes hydroxide ions or carbonate ions; The alkaline washing solution comprises a first reducing agent with a mass fraction of 0.1-10 wt% and an alkaline substance with a mass fraction of 2-20 wt%, and the water washing solution comprises a second reducing agent with a mass fraction of 0.5-15 wt% and water. The first reducing agent and the second reducing agent each independently include at least one of glucose, oxalic acid, hydrazine hydrate, sodium sulfite, citric acid, oxalic acid, or D-iso-oxalic acid.

17. A manganese-rich cathode precursor, characterized in that, The manganese-rich cathode precursor is prepared by the preparation method according to any one of claims 1-16.

18. A positive electrode material, characterized in that, The cathode material is obtained by sintering the manganese-rich cathode precursor as described in claim 17 with a lithium source.

19. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material as described in claim 18.

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